Touch panels are usually used for input and output interfaces of information apparatuses, e.g., automatic teller machines (ATMs), cashers, and interactive multimedia stations. Touch panels may be categorized as pressure-sensitive touch panels, resistance type touch panels, surface sound wave type touch panels, capacitance touch panels, and infrared touch panels.
For optical touch panels such as infrared touch panels, a number of infrared emitting devices and a number of infrared receiving devices are mounted on the printed circuit board thereof. The shape of the printed circuit board is rectangular, and the inner area of the printed circuit board is removed. Along one pair of opposite strips of the printed circuit board, the infrared emitting devices and the infrared receiving devices are mounted and aligned to each other, and along the other pair of opposite strips of the printed circuit board, the infrared emitting devices and infrared receiving devices are mounted and aligned to each other. The aligned infrared emitting devices and infrared receiving devices define a matrix of intersecting light beams that coincide with the graphical icons and the computer-generated graphics at the infrared touch panel. When the intersecting beams are disrupted by an object (e.g., the finger of a user), the position at which the disruption occurs may be precisely calculated.
FIG. 1 shows a printed circuit board 100 of an infrared touch screen panel according to the prior art. The printed circuit board 100 may be a rectangular printed circuit board, wherein an inner area 104 is removed to provide a touch screen area. The infrared touch panel is constructed from a number of infrared emitting devices 108, 112 and a number of infrared receiving devices 116, 120 mounted on the printed circuit board 100. The infrared emitting devices 108 and the infrared receiving devices 116 are aligned to each other along one pair of opposite strips of the printed circuit board 100, and the infrared emitting devices 112 and the infrared receiving devices 120 are aligned to each other along the other pair of opposite strips of the printed circuit board 100. The aligned infrared emitting devices and infrared receiving devices 108, 116 and the aligned infrared emitting devices and infrared receiving devices 112, 120 define a matrix of intersecting light beams. The above components are further assembled with the frame (not shown in FIG. 1), the touch panel plate (not shown in FIG. 1), and the flat display panel (not shown in FIG. 1) to provide an infrared touch panel. In this conventional technology, the inner area 104 is to be removed from the printed circuit board 100. Thus, the material of the printed circuit board 100 is wasted considerably because of the removed inner area 104, and the manufacturing cost is relatively high.